Study On Preparation And Heat Generation Of Modified Silica/Natural Rubber Composites

Silica is an important filler and its use level second only to carbon black in rubber industry.Silica-filled tire rubber shows lower heat build-up,lower rolling resistance and higher wet skid resistance compared to traditional filler carbon black.However,with a large number of hydroxyl groups on the surface,polar silica is difficult to disperse in the non-polar rubber matrix,and the processability of silica is poor and it is difficult to mix with rubber,causing dust pollution,which is one of the main reasons limiting the development of silica.In view of the above problems,silica/natural rubber masterbatch was prepared by a new method between dry and wet mixing technology.Compared with silica,silica-NRL masterbatch simply and efficiently solved the problems of processing difficulties and poor dispersion of high filled silica and reduced the energy consumption during processing.The effects of different modification methods and high filling silica on dynamic heat generation performance of composites were investigated.Partial replacement of silica with aramid pulp makes sure that the heat build-up of the composite can be reduced while the mechanical properties remain unchanged.“Deforming transformation” was proposed.The main content has the following aspects:(1)The silica was modified by silane coupling agent(KH570,KH580,Si69),and the modified silica/natural rubber composites were prepared.The properties of unmodified silica and different silane coupling agents modified silica filling natural rubber and the effects on dynamic heat generation of composites were studied.The results shown that after modifying with silane coupling agent,the interaction between silica was reduced and the combining capacity between silica and rubber molecular chain was enhanced,thus improved the equivalent crosslinking density,mechanical properties and reduced the heat build-up and "Payne" effect of the modified silica/natural rubber composite.(2)The silica/natural latex(silica-NRL)masterbatch was prepared,which was used to prepare silica/natural rubber composites.The properties of untreated silica and silica-NRL filled natural rubber composites were compared.The effect of different content of natural latex on the properties of silica/natural rubber composite was investigated.The results shown that after natural latex pretreatment,the processability was improved which solved the problem of difficulty mixing silica with rubber.The dispersion of silica was improved and the "Payne effect" of composites was reduced.It was found that the dynamic heat generation performance of the composites was directly proportional to the content of natural latex,that is,the higher the content of natural latex was,the better the dispersion performance of white carbon black was,and the lower the dynamic heat generation of the composite was.(3)High filling silica/natural rubber composites were prepared by using silane coupling agent Si69 and natural latex.The properties of processing of silica and(silica-NRL)masterbatch were compared and the effects of different content of natural latex on the properties of silica/natural rubber composite were investigated.The results show that because of the synergistic action of silane coupling agent(Si69)and natural latex,the properties of silica-Si69-NRL/natural rubber composite are higher than those of silica/natural rubber or silica-NRL/natural rubber composite.The natural latex can significantly improve the processability of silica,and when the content of silica is loaded to 60 phr,it still shown good processability.High filling silica/natural rubber showed excellent mechanical properties and anti-skid properties,but the heat build-up is higher.The silica/natural rubber composite,loaded 40 phr silica treated with silane coupling agent Si69 and natural latex,shows the lowest heat build-up.(4)Partial replacement of silica with modified fibers(AP-NRL)was used to prepare AP/silica/NR composites.The feasibility of replacing part of silica with a small amount of aramid fiber and its effect on heat generation performance of AP/silica/NR composite were studied.The results show that the mechanical properties of fiber filled composites can be improved effectively.Compared with silica/NR only filled 50 phr silica,the performances of AP/silica/NR composites which replacement of 5phr silica with 1phr AP were all improved.The 100% and 300% constant elongation stress of the AP/silica/NR composites with 2phr AP replacing 10 phr silica increased significantly,and the mechanical properties were still outstanding after 50,000 cycles of fatigue.The dynamic heat generation of the composites was reduced by using the "deformation transfer effect".Summed up,the feasibility of using fiber instead of silica is confirmed.